An MTJ in an MRAM array or TMR read head is disclosed in which a low magnetization capping layer is a composite having a NiFeHf inner layer formed on a NiFe or CoFeB/NiFe free layer, a Ta middle layer, and a Ru outer layer on the Ta layer. For example, a low magnetization NiFeHf layer is achieved by co-sputtering NiFe and Hf targets with a forward power of 400 W and 200 W, respectively. A higher Hf content increases the oxygen gettering power of the NiFeHf layer and the thickness is modified to change dR/R, RA, and magnetostriction values. A so-called dead layer between the free layer and capping layer is restored by incorporating a NiFeHf layer on the free layer to improve lattice matching. The Fe content in the NiFe target used to make the NiFeHf layer is preferably the same as in the NiFe free layer.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An MTJ element formed between a bottom conductor layer and a top conductor layer in a magnetic device, comprising: a stack of layers comprising a pinned layer, tunnel barrier layer, and a free layer wherein said free layer has a surface comprised of NiFe S alloy opposite the tunnel barrier layer and contacting a composite capping layer where s is the atomic % of Fe in the NiFe S alloy; and a composite capping layer wherein said capping layer is comprised of a low magnetization NiFeHf layer that contacts the surface of the NiFe S free layer opposite the tunnel barrier layer, said low magnetization NiFeHf layer has a NiFe composition equivalent to that in the NiFe S alloy.
2. The MTJ element of claim 1 wherein the magnetic device is an MRAM and the free layer is comprised of NiFe, or wherein the magnetic device is a TMR read head and the free layer has a FeCo/NiFe or FeCoB/NiFe configuration.
3. The MTJ element of claim 1 wherein the composite capping layer is further comprised of a Ta layer formed on the low magnetization NiFeHf layer and a Ru layer on the Ta layer.
4. The MTJ element of claim 1 wherein the MTJ element is comprised of a seed layer, AFM layer, pinned layer, and tunnel barrier layer that are sequentially formed on the bottom conductor, said free layer is formed on the tunnel barrier layer.
5. The MTJ element of claim 4 wherein the tunnel barrier is made of AlOx, AlTiOx, or MgO and the free layer is comprised of NiFe.
6. The MTJ element of claim 4 wherein the tunnel barrier is comprised of MgO and the free layer has a FeCoB/NiFe configuration.
7. The MTJ element of claim 1 wherein said low magnetization NiFeHf layer has a thickness from about 10 to 50 Angstroms.
8. The MTJ element of claim 2 wherein the Fe content in said low magnetization NiFeHf layer and in the NiFe free layer is from about 8 atomic % to 21 atomic %.
9. An MTJ element formed between a bottom conductor layer and a top conductor layer in a magnetic device, comprising: a stack of layers comprising a pinned layer, tunnel barrier layer, and a free layer wherein said free layer has a surface opposite the tunnel barrier layer and is comprised of a lower CoFeB layer and an upper NiFe layer to give a CoFeB/NiFe configuration; and a composite capping layer wherein said capping layer is comprised of a low magnetization NiFeHf layer that contacts the surface of the upper NiFe free layer opposite the tunnel barrier layer.
10. The MTJ element of claim 9 wherein the composite capping layer is further comprised of a Ta layer formed on the low magnetization NiFeHf layer and a Ru layer on the Ta layer.
11. The MTJ element of claim 9 wherein the MTJ element is comprised of a seed layer, AFM layer, pinned layer, and tunnel barrier layer that are sequentially formed on a substrate, said free layer is formed on the tunnel barrier layer.
12. The MTJ element of claim 9 wherein the tunnel barrier is made of AlOx, AlTiOx, or MgO.
13. The MTJ element of claim 9 wherein said low magnetization NiFeHf layer has a thickness from about 10 to 50 Angstroms.
14. The MTJ element of claim 9 wherein the Fe content in said low magnetization NiFeHf layer and in the NiFe free layer is from about 8 atomic % to 21 atomic %.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
July 31, 2006
September 29, 2009
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